I'm building a 393 motor for a 1988 F150 4x4. The truck has a 5 speed ZF trans, 3.54 gears, and 33" tires. The engine will have a cast crank and hyper pistons at about 9.5:1 static compression / ARP bolts throughout. Heads will be World Products Windsor Sr. cast iron with Manley stainless 2.02 intake / 1.60 exhaust / 200 cc runners / springs good to .600. Intake is a Edelbrock Performer, and carb is an Edelbrock Performer 600cfm. Exhaust will be Hooker headers to 2-1/2" turbo mufflers and then 2-1/2" pipes out the back. My intent is to never turn the engine over 5000-5500 rpm. The truck will be a daily driver and will be used to tow from time to time.

My question is:

What hydraulic cam will work best for this setup? (I am prepared for different opinions)

I have been looking at cams in the .475/.500 lift, 225@.050 duration range. Is that too big?

Thanks. Mark.

 

Has anyone built anything similar that could give me some ideas? Thanks. Mark.

 

My motor is pretty similar to yours.

My cam stinks...I hate it....my cam is

480/501 lift 210/216 duration at .050. With my 1.72 rockers my lift comes out to about 516/538. (intake/exhaust).

My cam was put in by CHP when I got the shortblock, and I'd like to swap it out for something else, still working on that.

Basically my cam doesn't have enough duration to keep the valves open long enough. I'm only making 220hp and 330tq.

Best thing you can do is call Comp Cams for their recommendation. They'll ask you what your setup is and will give you a couple recommendations.

 

I called Comp Cams. The guy I talked to gave me the impression that he didn't like Fords, and he didn't like trucks. He recommended a cam even smaller than what you are running... basically a stock 351W grind. I didn't understand that because I told him I wanted something that would pull hard to 5000 rpm. He just wasn't much help, so I was hoping someone here had built an engine for similar use and knew of a good cam. Thanks. Mark.

 

call cammotion. that carb will be to small as well you will need at least a 750

 

I'm curious why this carb is too small. The carb and intake are specifically what Edelbrock recommended for this build based upon the cam I had proposed to use which I posted above. Thanks. Mark.

 

Your engine will put out about 400-450+ horses, definitely dont want to be under-carbed. I think that 600 is pretty low myself.


Maybe you just struck out with that one rep from compcams, they make all sorts of truck cams and are very helpful more often then not. Sounds like that guy shouldn't be working there if he's biased to another manufacturer.

 

In the begining I thought I would need more carb, too. But the guy at Edelbrock took all my information and plugged it into some formula they use. He said the "perfect" carb for my setup was about 570cfm, so he told me to buy the 600. He also said that the 750 was "way too big" in his words. I am begining to wonder if these companies have anyone who really knows anything. Thanks for the help. Mark.

 

You can't trust what a company says at all....its always best to get several opinions.

Like if I went to comp cams for their recommendation, I'd probably talk to 2 different reps and see what either of them had to say...then checked on the forums for other peoples opinions and see if they match. I wound up with the wrong cam in my engine.

The guy I went through at CHP to get my motor screwed up a TON of things on me...turned my motor project into a 9 month PITA.

 

a 390 fe motor should have at least a 750 cfm on it. and those motors arnt considered hi hp motors either. you told them that this is for a truck right?

 

For perspective, a stock 4.2L I-6 jeep motor has a 400 CFM carb on it. I think it's about 120hp lol.

 

Actually I just called them back to see if they would admit a mistake. They stand by their original recommedation. Here is the formula they told me to use:

((cubic inches X RPM)/3456) X VE%) = carb CFM

where VE% is volumetric efficientcy (which for ease of calculation we will call 100% or 1.0, although they said my VE would not be over 95%)

so for me: 393X5000=1965000 divided by 3456 = 568 X 1.0 = 568

I told them it seemed small, but I really couldn't argue with the math. They assured me it would work perfectly. I hope the carb works out since it's already bought, but what about a cam recommendation?

Thanks. Mark.

 

I've found over the years that mathematical formulae don't always correspond to real-world results. A 600cfm carb is about right for a mildly built 302, (I run a 650 on my Tiger) so I would have to agree with Justin and Kemicalburns on this one...you're gonna be undercarbed with a 600. Yeah, you can still run it, you just won't be using all the potential of your engine.

And you might try calling a few other cam companies for their recommendations as well. I talked to guy at Crane a few months ago who actually seemed to be fully-evolved life form.

Try reading this article: https://www.ford-trucks.com/article/...arburator.html

Good luck, -TD

 

Look at how close you are....568 CFM. You've suppositly only got 32 CFM to spare, according to the formula. Your engine will spin above 5000. Mine spins to 6000.

6000 RPM would need 682 CFM. You're not going to get the best power out of it by cutting it 32 CFM short of the rated flow. That engine will be struggling to breathe. Think about it....it'll work fine...but it won't give you the best performance. Edelbrock is biased, maybe they make more money on the 600 carbs...I duno...but 600 ain't enough to get great power from. It doesn't make much sense to spend all that dough on a nice engine and then just choke some of it's power. I just encourage you to get other people's opinions and by all means don't just take my word for it, but I have a good feeling we're right.

 

From all I've read and heard, 600 cfm should work fine if it's just a daily driver motor and rarely raced, it may even be more efficient than a 750 carb. If you will be regularly up in higher rpms than go for the 750.

Remember that Chev 350s came with 750s many years ago and the general consensus was that they were overcarbed.